Effect of tin oxide nanoparticle binding on the structure and activity of α-amylase from Bacillus amyloliquefaciens

Inhibition of α-amylase digestion by a Lonicera caerulea berry polyphenol starch complex revealed via multi-spectroscopic and molecular dynamics analyses

Polyphenol-starch complexes exhibit synergistic and beneficial effects on both polyphenols and resistant starches. This study evaluates the inhibitory effects and mechanisms of α-amylase on a Lonicera caerulea berry polyphenol-wheat starch (LPWS) complex following high hydrostatic pressure treatments of 400 MPa for 30 min and 600 MPa for 30 min. The IC50 values for α-amylase inhibition by the complex were 3.61 ± 0.10 mg/mL and 3.42 ± 0.08 mg/mL at a 10 % (w/w) polyphenol content. This interaction was further supported by Fourier-transform infrared spectroscopy and circular dichroism, which confirmed that the alpha helix component of the secondary structure of α-amylase was reduced due to the complex. Multifluorescence spectroscopy revealed that the complex induces changes in the microenvironment of fluorophores surrounding the α-amylase active site. Molecular dynamics simulations and molecular docking revealed that the active site of amylose within the complex becomes enveloped in polyphenol clusters. This wrapping effect reduced the hydrogen bonds between amylose and α-amylase, decreasing from 16 groups to just one group. In summary, the LPWS complex represents a low-digestible carbohydrate food source, thus laying the groundwork for the research and development of functional foods aimed at postprandial hypoglycemic effects.

Graphene oxide/chitosan composites as novel support to provide high yield and stable formulations of pectinase for industrial applications

An extracellular pectinase from a mixed consortium of Bacillus sp. (BSP) was immobilized onto graphene oxide/chitosan composite (GO/CS) through covalent binding to enhance its recycling and operational stability features. Different parameters were optimized, including cross-linker concentration (%), time, pH, and GO/CS-pectinase ratios. GO/CS-pectinase was further characterized by FT-IR and XRD. The activity of GO/CS-pectinase was reached up to 804 μmolmin^-1 with an immobilization efficiency of 80.64 ± 1.15 % under optimum conditions. GO/CS-pectinase exhibited a 3.0-folds higher half-life (t_1/2) than free pectinase at 50, 55, and 60 °C, respectively. The V_max and K_M values of GO/CS-pectinase were found to be nearly equal to the free pectinase indicating that conformational flexibility was retained. K_d, t_1/2, ∆G*, ∆H*, and ∆S* of both free pectinase and GO/CS-pectinase was 0.0339 & 0.0721 min^-1, 9.62 and 40.44 min, 81.35, 90.72 kJmol^-1, 47.098 & 63.635 kJmol^-1, -102.86 & -81.340 Jmole^-1 K^-1. SEM morphological analysis further confirmed the successful binding of pectinase with GO/CS, which retained about 92 % of its original catalytic activity after ten consecutive reaction cycles. Finally, GO/CS-pectinase was employed for guava juice clarification which exhibited the turbidity reduction up to 81 % after 75 min of treatment.

Industrial applications of immobilized nano-biocatalysts

Immobilized enzyme-based catalytic constructs could greatly improve various industrial processes due to their extraordinary catalytic activity and reaction specificity. In recent decades, nano-enzymes, defined as enzyme immobilized on nanomaterials, gained popularity for the enzymes' improved stability, reusability, and ease of separation from the biocatalytic process. Thus, enzymes can be strategically incorporated into nanostructured materials to engineer nano-enzymes, such as nanoporous particles, nanofibers, nanoflowers, nanogels, nanomembranes, metal-organic frameworks, multi-walled or single-walled carbon nanotubes, and nanoparticles with tuned shape and size. Surface-area-to-volume ratio, pore-volume, chemical compositions, electrical charge or conductivity of nanomaterials, protein charge, hydrophobicity, and amino acid composition on protein surface play fundamental roles in the nano-enzyme preparation and catalytic properties. With proper understanding, the optimization of the above-mentioned factors will lead to favorable micro-environments for biocatalysts of industrial relevance. Thus, the application of nano-enzymes promise to further strengthen the advances in catalysis, biotransformation, biosensing, and biomarker discovery. Herein, this review article spotlights recent progress in nano-enzyme development and their possible implementation in different areas, including biomedicine, biosensors, bioremediation of industrial pollutants, biofuel production, textile, leather, detergent, food industries and antifouling.

Identification of fungi in Tunisian olive orchards: characterization and biological control potential

Background

Olive production is the main agricultural activity in Tunisia. The diversity of fungi was explored in two different olive groves located in two distant geographical zones in Sfax (Tunisia) with different management practices.

Results

Fungal isolation was made from soil and the major olive tree pests, namely the Olive fly, Bactrocera oleae Gmelin (Diptera: Tephritidae), and the Olive psyllid, Euphyllura olivina Costa (Homoptera: Psyllidae). A total of 34 fungal isolates were identified according to their phenotypic, genotypic, biochemical and biological activities. Twenty fungal species were identified belonging to six different genera (Alternaria, Aspergillus, Cladosporium, Fusarium, Lecanicillium and Penicillium) by the analysis of their ITS1–5.8S–ITS2 ribosomal DNA region. Different bioassays performed in this work revealed that 25/34 (73.5%) of the identified fungal isolates showed an entomopathogenic and/or antagonistic activity, 9/34 (26.5%) of them displayed phytopathogenic features.

Conclusions

Fungal species that showed entomopathogenic and/or antagonistic potentialities and that are non-phytopathogenic, (17/34; 50%) of our fungal isolates, could be explored for olive protection against fungal diseases and pests, and might have a future application as biocontrol agents.

Screening of biological activities of fungi associated with pistachio bark beetle, Chaetoptelius vestitus (Coleoptera, Curculionidae), infesting pistachio cultivations in Tunisia

AIMS

In this study, we aimed to explore the enzymatic diversity, the entomopathogenic and the antimicrobial potentialities of fungi associated with the pistachio bark beetle, Chaetoptelius vestitus.

METHODS AND RESULTS

A total of 40 isolates were screened for enzymatic diversity. Most of them, 92·5%, were able to produce at least two of the screened enzymes. Pathogenic assays performed on C. vestitus showed a high entomopathogenic activity of the isolates Ata_io_1 (A. tamarii), Fve_io_1 (F. verticillioides), Tpi_io_1 (T. pinophilus), Pal_io_1 (P. album), Pbi_io_2 (Penicillium bilaiae) and Pch_io_1 (P. chrysogenum), as based on mean mortality of C. vestitus. A screening of antimicrobial activity using well diffusion method showed that the isolates Tro_io_1 (T. pinophilus), Tat_io_1 (T. atroroseus) and Pch_io_1 (P. chrysogenum) presented the highest antibacterial activity. Furthermore, Mgu_io_1 (M. guilliermondii), Asc_io_1 (A. sclerotiorum), Ata_io_1 (A. tamarii), G. lavendula (Gla_io_1), Pva_io_1 (P. variotii), Pul_io_1 (P. ulaiense), Tat_io_1 (T. atroroseus) and Tro_io_1 (T. roseum) were active against at least two of the three tested fungal phytopathogens.

CONCLUSIONS

Fungal isolates representing entomopathogenic activity and a broad spectrum of antimicrobial activities can be considered as promising resources for biological pistachio trees protection.

SIGNIFICANCE AND IMPACT OF THE STUDY

Fungi associated with C. vestitus were investigated for detecting their potential biotechnological applications.

Screening of bacterial isolates related to olive orchard pests in Tunisia using 16S ribosomal RNA and evaluation of their biotechnological potential

AIM

This study investigated the bacterial diversity of dead insects collected from olive tree orchards widely cultivated in Tunisia. We aimed to explore metabolic diversity, screen enzymatic activities for biotechnological applications and carry out preliminary bioassays for bio-insecticide development.

METHODS AND RESULTS

A total of 50 bacteria strains were randomly isolated from four different biotopes situated in Sfax (Tunisia). 16S rRNA gene sequencing was used to identify 24 species, and isolates were evaluated for enzymatic activity and antimicrobial potential. Nineteen of the total number of Bacillus strains have enzymatic activity compared to strains from the other genera (14/50). Our bacterial collection was evaluated for antimicrobial potential against bacterial and fungal isolates. Isolates B8-2 (Bacillus subtilis) showed strong antibacterial activities and isolates B2-3 (Bacillus licheniformis) and B10-1 (Serratia marcescens) showed the highest antifungal activity. Seventeen of the total number of isolates caused greater than 50% mortality rate of second and fourth instar larvae of Ephestia kuehniella.

CONCLUSION

The selected species from olive orchards represent a broad spectrum of antimicrobial and insecticidal activities and can be considered promising resources in biological control.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bacteria isolated from olive pests in olive orchards were investigated for detecting their potential biotechnological applications.

Inhibitory effect of epigallocatechin-3-O-gallate on α-glucosidase and its hypoglycemic effect via targeting PI3K/AKT signaling pathway in L6 skeletal muscle cells

Epigallocatechin-3-O-gallate (EGCG), a tea polyphenol is renowned for its anti-diabetic properties, however limited studies elucidate its hypoglycemic mechanism from multi-perspectives. In the present study, the interaction between EGCG and α-glucosidase was investigated through kinetics analysis, fluorescence spectra, Fourier transform infrared (FT-IR) spectra and molecular docking studies. Additionally, the effect of EGCG on glucose uptake and its related signaling pathway in L6 muscle cells were also investigated. The results showed that the α-glucosidase inhibitory activity of EGCG (IC₅₀ = 19.5 ± 0.3 μM) was higher than that acarbose (IC₅₀ = 278.7 ± 1.1 μM). EGCG inhibited α-glucosidase in a reversible and non-competitive manner. EGCG quenched the fluorescence of α-glucosidase due to the complex formation between EGCG and α-glucosidase, where the hydrogen bonds played a critical role. Microenvironment and the secondary structure of α-glucosidase were highly influenced by EGCG. Molecular docking results indicated that the binding sites on α-glucosidase for EGCG were close to the active site pocket of the enzyme. EGCG was also found to enhance the glucose uptake and promote GLUT4 translocation to plasma membrane via PI3K/AKT signaling pathway in L6 skeletal muscle cells. Overall, these results revealed the possible hypoglycemic mechanism of EGCG.

Nano-gold displayed anti-inflammatory property via NF-kB pathways by suppressing COX-2 activity

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease, affecting almost 1% of world population. Although the exact cause of RA is not known but the complex interaction between inflammatory mediators like tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2) and nitric oxide (NO) is accountable for cartilage destruction in joints. Gold is used for arthritis treatment since long without knowing its mechanism of action. Hence, the present study was designed to assess antiarthritic activity of nanogold (AuNGs) in collagen-induced arthritic (CIA) rat model by virtue of decreasing inflammatory mediators and oxidative stress. After induction CIA rats were treated with AuNGs in phosphate buffer at a dose of 20 μg/kg body weight for 20 days and found a significant decrease in the level of inflammatory mediators like TNF-α, IL-1β, COX-2 and transcription factor NF-kB (Nuclear factor-kB), which was found to be elevated in CIA rats. Additionally imbalance in oxidant and antioxidant status were determined and perceived that AuNGs remarkably attenuates the imbalance in level of antioxidant and oxidant near to normal. In consistent to biochemical results, mRNA expression of NF-kB, TNF-α, COX-2, and iNOS were also up-regulated in CIA rats, which were considerably down regulated by AuNGs treatment. These findings were positively correlated with the histological results of joints, displayed reduced inflammation and bone erosion in treated group. This study demonstrates the ability of AuNGs to ameliorate production of inflammatory mediators and oxidative stress in CIA rats. Induction of arthritis in rats showed increased inflammation, which activate the transcription factor NF-kB through activation of of IkB kinases (IKK) and ubiquination/proteosome degradation of IKB and transportation of activated NF-kB from cytoplasm to nucleus. In nucleus activated NF-kB bind to the promoter region of target gene and up regulate the production of pro-inflammatory cytokines, COX-2 and other inflammatory mediators that leads to cartilage destruction. AuNGs inhibit the activation of NF-kB and other inflammatory mediators and attenuate inflammation and cartilage destruction. COX-2: cyclooxygenase-2; IKK: IkB kinases; IKB: I Kappa B; IL-1β: interleukin-6; IL-6: interleukin-6; iNOS: inducible nitric oxide synthase; NF-kB: nuclear transcription factor kappa B; ROS: reactive oxygen species; TNF-α: tumour necrosis factor-alpha.

In vitro inhibition of pancreatic α-amylase by spherical and polygonal starch nanoparticles

Nanoparticles are novel and fascinating materials for tuning the activities of enzymes.

Aggregation behavior of TiO2 nanoparticles in municipal effluent: Influence of ionic strengthen and organic compounds

The influence of ionic strengthen and dissolved organic matter (DOM) on the aggregation of TiO₂ nanoparticles (NPs) in municipal effluent was investigated. The results demonstrated that DOM promoted the mobility of NPs in aquatic system by synergism between static repulsion and steric effect, while electrolytes were opposite by charge-neutralization. The physical-chemical characteristics of DOM played the major role on the mobility of NPs. Bovine serum albumin (BSA) showed the strongest enhancement on the mobility of TiO₂ NPs. High adsorption of BSA introduced vast negative charges on the TiO₂ NPs' surface, leading to static repulsion and neutralizing positive charges of electrolytes in surrounding as well. By contrast, another protein α-amylase retarded the aggregation rate of TiO₂ NPs through steric repulsion of the long-chain construction. Humic substances (Fulvic acid and alginate) also reflected the combination of static repulsion and steric effect. However, in the high electrolytes concentration (especially Ca²⁺), the long-chain aliphatic compounds were prone to form calcium bridge which increased the hydrodynamic diameter of TiO₂ aggregates consequently. Sodium dodecylbenzene sulfonate (SDBS) showed low adsorption capacity, while the unabsorbed SDBS retarded the aggregates caused by the changes of pH and electrolytes. These data indicated that decreasing of DOC concentration in aqueous system was important to reduce the mobility and potential risk of NPs in aqueous system.

Nanomaterials as novel supports for the immobilization of amylolytic enzymes and their applications: A review

Numerous types of nanoparticles and nanocomposites have successfully been employed for the immobilization and stabilization of amylolytic enzymes; α-amylases, β-amylases, glucoamylases and pullulanases. Nano-support immobilized amylolytic enzymes retained very high activity and yield of immobilization. The immobilization of these enzymes, particularly α-amylases and pullulanases, to the nanosupports is helpful in minimizing the problem of steric hindrances during binding of substrate to the active site of the enzyme. The majority of nano-support immobilized amylolytic enzymes exhibited very high resistance to inactivation induced by different kinds of physical and chemical denaturants and these immobilized enzyme preparations maintained very high activity on their repeated and continuous uses. Amylolytic enzymes immobilized on nano-supports have successfully been applied in food, fuel, textile, paper and pulp, detergent, environmental, medical, and analytical fields.

Graphene based magnetic nanocomposites as versatile carriers for high yield immobilization and stabilization of β-galactosidase

The present study demonstrates an efficient method for high yield immobilization of Aspergillus oryzae β-galactosidase onto graphene-iron oxide nanocomposites (Gr@Fe₃O₄ NCs) by a simple adsorption mechanism.

Micrococcus luteus mediated dual mode synthesis of gold nanoparticles: involvement of extracellular α-amylase and cell wall teichuronic acid

In the present study we have utilized the bioreductive potential of Micrococcus luteus for the synthesis of gold nanoparticles. Biochemical and physiological analysis indicate that the biosynthesized GNPs were achieved by dual mode, involving extracellular α-amylase and cell wall teichuronic acid (TUA) of M. luteus. The biosynthetic potential of both α-amylase and TUA, after isolation from bacterium, was examined. Under optimum conditions, these biomolecules reduces Au(3+) into Au(0) and the resulting GNPs were found to be stable for 1 month. The synthesized GNPs were characterized by UV-VIS spectrometry, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS). Results demonstrated that the synthesized GNPs were found to be monodispersive and spherical in shape with an average size of ∼6 nm and ∼50 nm for α-amylase and teichuronic acid, respectively. These findings suggest that M. luteus can be exploited as a potential biosource for the eco-friendly synthesis of gold nanoparticles.